1. Field of the Invention
The present invention relates to a membrane switch, and more particularly to a membrane switch capable of turning on a switch with a small pushing force.
2. Description of the Related Art
Conventionally, a membrane switch is known which includes a lower film, a plurality of lower electrodes, an upper film, a plurality of upper electrodes, and a spacer film (Japanese Laid-Open Patent Publication (Kokai) No. H05-217463 (Paragraph numbers [0002] to [0010], FIG. 3).
The lower electrodes are formed at equal space intervals on the upper surface of the lower film.
The upper film is opposed to the lower film via the spacer film.
The upper electrode are formed at equal space intervals on the lower surface of the upper film.
A plurality of through holes are formed in the spacer film interposed between the upper film and the lower film. Each through hole accommodates a pair of a lower electrode and an upper electrode opposed to each other.
In this membrane switch, when a push portion of the upper film is pushed, an upper electrode under the push portion is brought into contact with a lower electrode associated therewith to turn on the switch.
The size of the push portion of the upper film is larger than that of the upper electrode. A gap between the lower electrode and the upper electrode is relatively large so as to prevent the lower electrode and the upper electrode from being erroneously brought into contact with each other when the membrane switch is bent.
In the above-described membrane switch, to bring an upper electrode into contact with a lower electrode associated therewith, it is required to push a small push portion with a fingertip to largely bend the push portion, which necessitates a large pushing load. This makes the membrane switch low in operability.